The cellular receptors that allow Anthrax interaction with host are proposed to be angiogenic receptors. Understanding their function may be critical in designing strategies to interfere with Anthrax toxin action. For instance, reagents that block anthrax-receptor interaction may interfere with native ligand-receptor interactions thus affecting vessel integrity, angiogenesis and epidermal cells. This proposal defines the angiogenic functions of the receptor with highest affinity for the anthrax protective antigen (PA), that is ANTXR2/CMG2. The function of ANTXR2/CMG2 will be studied in tissues sites of anthrax exposure, specifically skin. Our preliminary studies shows that ANTXR2/CMG2 is important for capillary-like tube formation, proliferation and migration of endothelial cells. We describe sites of ANTXR2/CMG2 expression of relevance to Anthrax exposure and we demonstrate that a soluble form of the extracellular domain of CMG2 inhibits VEGF-driven neovascularization in skin. Our emphasis here will be on ANTXR2/CMG2 function in dermal angiogenesis, in keratinocyte function and on anthrax protective antigen (PA) binding to such cells. Our overall objective is to understand ANTXR2/CMG2 function in cells of the skin, in order to study the consequence of inhibition of anthrax toxin/receptor interaction on host cell function. To achieve this objective, in Aim I we evaluate ANTXR2/CMG2 function in dermal microvascular endothelial cells, using knockdown and receptor antagonists to interfere with function. We hypothesize that ANTXR2/CMG2 promotes key steps in dermal angiogenesis. This hypothesis will also be evaluated in Aims II and III that focus on in vivo assessment of ANTXR2/CMG2 function during vascular development, dermal angiogenesis induced by VEGF and during wound repair. In Aim III we will conditionally ablate ANTXR2/CMG2 expression. Our preliminary results show that ANTRX2/CMG2 is expressed in diverse cell types thus we will conditionally remove gene function in endothelial cells or keratinocytes, both potential sites of anthrax interaction. Finally, in Aim IV we test the hypothesis that ANTXR2/CMG2 serves as the major anthrax receptor in endothelium by evaluating PA-receptor interaction in knockdown endothelial cells and mutant mice with endothelial-specific loss of receptor expression.